Simulation of a software phaselocked loop for typical. The stepwise elaboration of the model illustrates how simulink forms the basis a modelbased design where continuous verification of the model reduces. I am submitting herewith a thesis written by akila gothandaraman entitled design and implementation of an all digital phase locked loop using a pulse output direct digital frequency synthesizer. A phase locked loop or phase lock loop pll is a control system that generates an output signal whose phase is related to the phase of an input signal. Phase lock loop pll elimination in grid synchronization and removal of switching. Loop filter the next stage after the phase detector is the loop filter. Im trying to design an analog phase locked loop in matlab. The default filter is a chebyshev type ii filter whose. Software phase locked loop design using c2000 microcontrollers for single phase grid connected inverter a functional diagram of a pll is shown in figure 1, which consists of a phase detect pd, a loop filter lpf, and a voltage controlled oscillator vco. Modeling and characterization of alldigital phaselocked loop. Ive read around and there are a few examples of this out there but im not sure how a few things work or how to adapt it for my use. This block is most appropriate when the input is a narrowband signal. You specify the filters transfer function in the block mask using the lowpass filter numerator and lowpass filter denominator parameters.
Implement charge pump phaselocked loop using digital. Introduction to phase lock loop system modeling by wen li, senior system engineer, advanced analog product group and jason meiners, design manager, mixedsignal product group, texas instruments incorporated 1. A pll consists of a phase detector, a lowpass filter, a variable frequency oscillator, and a divider figure 1. Here i show how to simulate phase locked loops plls with matlab. Once the in phase and quadrature signals are separated out properly, the next task is to match each symbol with the transmitted pulse shape such that the overall snr of the system improves. Analogue or digital in pll design electronics weekly. The phase angle of the utility is a critical piece of information for the operation of power devices feeding power into the grid like pv inverters. Examples of such systems include phase lock loops, clock data recovery, and analogto digital converters. These devices are being utilized in software defined radio, dspbased designs and many other communication and electronic systems to implement complex highspeed algorithms. Run the command by entering it in the matlab command window. In a previous article i introduced the fundamental concepts and the core functionality of a negativefeedback system known as a phase locked loop pll. Graduate program in electrical and computer science. The adpll has 50cycles lock time and a duty cycle distortion of less than 2%.
Matlab code for a simple phase lock loop pll kp and ki are two parameters about secondorder filter. To minimize these costs, engineers need a way to predict whether the design will meet specifications before implementing the design on silicon. In the weatherfax project, one of the key design issues was to convert a range of audio tones into a video signal, essentially fm detection. To lock the output phase of the sawtooth waveform to the reference signal, a digital phase locked loop is designed to lock all three harmonics to the external reference signal. The model should be able to perform accurate and time effective simulations. During a lengthy design and testing phase i evaluated most known methods for fm demodulation, beginning with a crude method that counted clock cycles between zero crossings, then a system of bandpass filters, and finally i designed a phase locked loop. This will get you started, but you really need to understand the fundamentals of pll design well enough to build it yourself in order to troubleshoot it later this is the realm of digital signal processing, and while not black magic it will certainly give you a run for your money during debugging.
Pr controller implementation using double update mode. Design and implementation of an all digital phase locked loop. The oscillator generates a periodic signal, and the phase detector compares the. I am working on a project about a frequencyhopping tranceiver. Also, circuit simulations are performed using topspice and matlab toolboxes. I did not have success using a two stage single pole low pass filters. In the linearized, phase domain analytical model, each component is represented by a matlab transfer function. The software receiver follows the most commonly used gps receiver structure. Mar 12, 2018 this article presents an ltspice circuit that can be used to explore the behavior of a phase locked loop. In the tracking mode, you can think of the whole loop as being a linear system, where the input and output phase are related by the transfer function where gs is the response of the loop filter. The simulation and test results of the adpll are also presented to verify. For example, we can estimate the noise at the input to the controlled oscillator and use the model to understand how that noise affects the output.
In this assignment, you will design a simple digital pll with a singlepole loop filter. The thesis modeling and characterization of an all digital pll aims to create a behavioral model of an all digital phase locked loop adpll. The loop filter can be optimised for constant loop bandwidth and phase margin for both cases. In this assignment, you will code the pll in c for the dsp board.
This tutorial starts with a simple conceptual model of an analog phaselocked loop pll. Matlab, simulink, signal processing toolbox, signal. Phaselocked loop makers of matlab and simulink matlab. I have looked among the blocks available and i havent found any for a pll or for a voltage controlled oscillator.
Mixing analog and digital signals matlab central blogs. Used to synchronize the phase of two signals, the phase locked loop pll is employed in a wide array of electronics, including microprocessors and communications devices such as radios, televisions, and mobile phones. Please read the background and answer the questions at the bottom under prelab exercise below. The output of the loop filter controls the frequency and phase of the nco, driving the phase error to zero. Design and simulate analog phase locked loop pll systems design a pll system starting from basic foundation blocks or from a family of reference architectures. In the digital domain the filter of choice is pid proportional, integral and derivative, actually just proportional and integral. However, with microcontrollers becoming faster, it may make sense to implement a phase locked loop in software for applications that do not require locking onto signals in the mhz range or faster, such as precisely controlling motor speeds. We create analytical and behavioral models of the adpll design in two domains. Below is the matlab program that simulates the above phase locked loop. Since the pll is a negative feedback system, phase margin and stability issues must be considered. How to simulate a phaselocked loop technical articles. A phase locked loop circuit responds to both the frequency and the phase of the input signals, automatically raising or lowering the frequency of a controlled oscillator until it is matched to the reference in both frequency and phase. Ece 5675 digital pll laboratory experiment 1 introduction the purpose of this laboratory exercise is to design, build, and experimentally characterize a second order digital phase lock loop dpll.
Software phaselocked loop based on virtual three phase. Through elaboration it ends at a model of an all digital and fixedpoint. Implementing a digital phaselocked loop in software digital phase locked loops can be implemented in hardware, using integrated circuits such as a cmos 4046. Digital phase lock loops then illustrates the process of converting the tdtl class of digital phase lock loops for implementation on an fpgabased reconfigurable system. Modeling and simulating an alldigital phase locked loop. Implement charge pump phase locked loop using digital phase detector. Based on the model, a sub block requirement will be presented as decision basis for test chip manufacturing. The loop bandwidth determines the frequency and phase lock time. Mathworks is the leading developer of mathematical computing software for engineers and.
Single phase digital pll design using tis delfino launchpad. Correct phase and frequency offset for 16qam using coarse and fine synchronization. A pll is an automatic control system that adjusts the phase of a local signal to match the phase of the received signal. Implementation of a 2ndorder dpll digital phase lock loop this section presents detailled information for implementing a completed dpll system based on the previous analysis and model mapping results. Time to digital ref t outt digital loop filter dco divt divider varactor varactor analog control dac. Design a pll system starting from basic foundation blocks or from a family of reference architectures.
At epoch microelectronics, we use matlab and simulink to ensure that our alldigital pll adpll design meets the specification before committing to hardware. The phase locked loop or pll is an electronic circuit with a voltage controlled oscillator, whose output frequency is continuously adjusted according to the input signals frequency. Allows the use of an existing vco within a digital pll. Design and simulate analog phaselocked loop pll systems. Symbol timing recovery for qpsk digital modulations. A phase locked loop is used for tracking phase and frequency of the input signal. Simulate and analyze the pll system to verify key performance metrics until you meet the system specifications. A digital phaselocked loop based llrf system sciencedirect. Nonlinear analysis of bpsk optical phaselocked loops using matlab and. The loop includes a phase detector to compute phase error and a loop filter to set loop dynamic performance. And when phase lock loop complete phase lock, the two phase is equal to one another 1 t 2.
Ill have more to say about the jwx project at the end of this article, but first lets discuss phase locked loops. Frequency synthesizers and digital divider analysistechniques have been added to this second edition. Well show how topdown pll design works in practice and provide examples of this method in use for commercial pll design. A phase locked looppll is an important component of many electronic devices and is a. Digitial, analog and optical implementations, second edition presents a complete tutorial of phase locked loops from analog implementations to digital and optical designs. A phase locked loop is a closed loop system in which an internal oscillator is controlled to keep the time and phase of an external periodical signal using a feedback loop. As its name implies, a phase locked loop pll is designed to lock the phase of an oscillator to the phase of a reference signal, providing a mechanism for synchronization on different platforms. Quadrature amplitude modulation using simulink project. Spectral purity of the pll output is specified by the phase noise and the level of the referencerelated spurs. Synchronization and receiver design carrier frequency and phase recovery, timing frequency and phase recovery, agc, iq imbalance compensation, phaselocked loops communications toolbox includes tools using either matlab or simulink for signal recovery. The phase locked loop pll block is a feedback control system that automatically adjusts the phase of a locally generated signal to match the phase of an input signal. Phase locked loop tutorial file exchange matlab central.
The digital part contains a gps antenna, an rf frontend, and an ad converter. A phase locked loop circuit responds to both the frequency and the phase of the input signals, which will automatically increase or decrease the frequency of a controlled oscillator until it is matched to the reference signal in both frequency and. Then make the phase of and approaching by pi control method. In this example our input signal will be simply a complex sinusoid without noise or modulated information. We start with an analytical model in matlab and then build a phase domain and timedomain model in. We start with an analytical model in matlab and then build a phasedomain and timedomain model in. Another important change is the increased use of matlab, implemented to provide more familiar graphics and readerderived phaselocked loop simulation. Software pll design using c2000 mcus single phase grid. A phaselocked loop pll, when used in conjunction with other components, helps synchronize the receiver. This pa per pr esen ts a dpll archi tectur e based on a direct. The fact that the phase locked loop is able to lock to a signal enables it to provide a clean signal, and remember the signal frequency if there is a short interruption. Software phase locked loop based on virtual three phase for power grid.
Applications of phase lock loop how phase lock loop works capture range and lock ran. Tracking is made of an iterative procedure during which the carrier loop and the code loop cooperate to provide the best estimate of the doppler frequency and of the code delay. This code will address a qam communication problem in. First of all, an architecture diagram of a 2ndorder dpll system is presented in fig. The phase locked loop approach turned out to be vastly superior to the other methods, to the degree that i want to describe the method in detail, so others wont pass up this terrific approach. Simulink is one of a small set of simulators that can naturally simulate analog and digital components in the same system. Ill be asking a lot of questions so feel free to answer one or all. To overcome the limitations of the simple digital delay circuit, a delay locked loop dll can be used instead. Cd74act297 digital phaselocked loop schs297d august 1998 revised june 2002 6 post office box 655303 dallas, texas 75265 detailed description continued thus, the simple firstorder phaselocked loop with an adjustable k counter is the equivalent of an analog. The purpose of the dpll is to lock the phase of a numerically controlled oscillator nco to a reference signal. One application of the dpll is to recover the timing in a digital demodulator. Through elaboration it ends at a model of an all digital and fixedpoint phaselocked loop. The output of the carrier loop is used to remove the modulation carrier wipeoff.
The related work, including the system design of the llrf control system and the development of the digital phase locked loop, are presented in this paper. Phase lock basics is a broadbased, handson text, designed to be both easy to understand and easy to customize. Interactive digital phase locked loop design this will get you started, but you really need to understand the fundamentals of pll design well enough to build it yourself in order to troubleshoot it later this is the realm of digital signal processing, and while not black magic it will certainly give you a run for your money during debugging. At epoch microelectronics, we use matlab and simulink to ensure that our alldigital pll adpll design meets the specification before committing to. The phaselocked loop pll block is a feedback control system that automatically adjusts the phase of a locally generated signal to match the phase of an input signal. I am multiplying the incoming signal with a certain frequency and passing it. The sine and cosine components are generated using a carrier recovery block phase lock loop pll or setting a local oscillator and tracking the variations. Software phaselocked loop based on virtual three phase for. The charge pump pll phase locked loop block automatically adjusts the phase of a locally generated signal to match the phase of an input signal. You can start by providing the specifications and impairments of each foundation block and connect the blocks to model different pll architectural models bottomup approach. To design a filter, use functions such as butter, cheby1, and cheby2 in signal processing toolbox software. When a, b, c, and d are programmed high, the k counter becomes 17 stages long, which narrows the bandwidth, or capture range, and lengthens the lock time. The text establishes a thorough foundation of continuoustime analysis techniques and maintains a consistent notation as discretetime and nonuniform sampling are presented.
The digital part containsn receiver channels and a position computation block. Implement charge pump phaselocked loop using digital phase. In power applications, we often require a pll to lock the grid frequency to be used for control applications. The dll is a phase locked device, so it tracks most variations in the input signal. Design of the controllers and their tuning methodology is elaborated and analysed through simulation in matlab. Each of these parameters is a vector that lists the coefficients of the respective polynomial in order of descending exponents of the variable s. The vco therefore integrates the control voltage to compute what the phase of its output sinusoid should be. Although direct digital synthesis is also used, indirect frequency synthesis forms one of the major phase locked loop applications. Also, the dll described here is a differential device, so it mitigates variations in supply voltage and temperature. A phase locked loop pll, when used in conjunction with other components, helps synchronize the receiver. Implement phaselocked loop to recover phase of input. Realtime control of loop bandwidth by manipulating the athroughd inputs can maximize the overall performance of the digital phase locked loop. Matlab code for a simple phase lock looppll kp and ki are two parameters about secondorder filter.
Design and implementation of an all digital phase locked. More importantly, the loop parameters can be adjusted by merely programming registers instead of changing components. Implementing a pll design on silicon can consume months of development time and hundreds of thousands of dollars in fabrication costs. Phase detector pd a phase detector is a device capable of generating a signal which is proportional to the phase difference between two signals, a multiplier is used usually 7. Prelab for the prelab, learn the background as usual and look at what is required in the prelab exercise below. The default filter is a chebyshev type ii filter whose transfer function arises from the command below. As a result, we can analyze the phase of the signal at each point in the loop. Through elaboration it ends at a model of an all digital and fixed point. The final model can serve a starting point for code generation both ansi c or synthesizable hdl. Pll loop dynamics closed loop transfer function of pll this is a second order system. Perrott 32 closed loop pll design approach classical open loop approachindirectly design gf using bode plots of af proposed closed loop approachdirectly design gf by examining impact of its specifications on phase noise and settling time solve for af that will achieve desired gf implemented in pll design assistant software lau and perrott. Can be applied across a broad range of ic processes.
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